It must be gratifying for a boxer when that first world title fight comes along. Especially when it has been earned.

Take Joseph Diaz Jr. of South El Monte. He told us two years ago he thought he was ready to fight for the featherweight championship. But he had to win six more times before his hard work would bear fruit.

The time has finally come, as Diaz on Saturday will challenge Gary Russell Jr. for his belt at MGM National Harbor in Oxon Hill, Md. (on Showtime).

It took Diaz 5 1/2 years to get here, after a fine amateur career that saw him box for Team USA in the 2012 London Games. He is 26-0 with 14 knockouts, and has fought his way to being the No. 1 contender to Russell’s WBC crown.

Diaz is over the moon about the way his odyssey has played out. He also admits there were some butterflies, knowing a misstep could derail him on his way to the promised land.

Diaz, a confident yet humble young man of 25, rarely puffs up his chest. Pardon him if he does this once.

“Every single day I wake up knowing that this spot wasn’t handed to me,” he said. “I went and I earned this spot. I earned becoming ranked in the WBC, making my way all the way in the rankings, becoming the mandatory to fight Gary Russell Jr.

“I wasn’t just picked. Gary Russell has to fight me because I’m mandatory, so I earned my spot to become this title challenger and it just gives me a lot of pride and a lot of happiness to know that with all the hard work, I’m finally here.”

Diaz recalled a conversation he had with manager Ralph Heredia around the time he was champing at the bit in 2016.

“Yeah, I felt like I was ready about two years ago,” Diaz said. “Me and my manager, Ralph, we were discussing it. But he was always telling me that I needed more experience and I needed to get that experience inside the ring with some tough, rugged opponents, guys that are going to bring out the best in me.

“And I was fighting young, hungry fighters.”

Heredia is also experiencing some emotion here.

“There’s a lot of pride because when you sign a fighter, this is what you dream of, to get him to this point,” he said. “Unfortunately, not too many horses make it to the Kentucky Derby, my man. And I believe this is one who is not only going to get to the Derby, but win it.”

Standing off to the side, and out earshot, was Joseph Diaz Sr., who is his son’s trainer. Unlike some fathers who train their sons, the elder Diaz prefers to stay completely out of the limelight.

But he couldn’t help but smile when the subject of his son truly earning this fight was broached.

“As far as him finally getting the title shot, knowing that he had to work his way up … nobody said, ‘OK, let’s pull him out of the No. 15 ranking,’” Joseph Diaz Sr. said. “He actually earned his spot and Gary Russell has to fight Joseph, not because he wants to fight him.

“To me, that’s an accomplishment in itself, just knowing that Joseph actually has worked his way to get to that point.”

Kind of stressful

Even though Diaz has been highly ranked for some time, had he lost a fight along the way, this title shot would not be coming Saturday. A fighter can have an off-night, he could lose to someone who was better than expected, he could fall victim to the proverbial lucky punch.

Diaz admitted it was a bit nerve-racking.

“Oh, absolutely,” said Diaz, who trains out of the South El Monte Boxing Club, which will host a viewing party Saturday night. “Every single fight, I knew that it was going to jeopardize my career if I lost. I knew that I had to train hard every single fight. So me and my father, my and my manager, we never took any of my opponents lightly.”

This is how an aspiring champion operates, and Heredia has never had one bit of trouble getting Diaz to adhere to that credo. At first, Heredia said he was not concerned anything would happen to hinder Diaz’s run to a title fight, because he knows Diaz.

“I was never nervous because I’ve been watching JoJo’s career from A to Z and I’ve seen the maturity, not only as a young man, but also as a fighter and how each opportunity got more challenging,” Heredia said. “He focused more and not only the focus, the determination that he wanted to succeed because he knew that each opponent was going to be getting tougher.”

But as Heredia kept talking, he came clean.

“So, to answer your question, I’m always nervous,” he said, laughing, also getting a laugh out of Diaz as they sat next to each other before a workout. “But as far as nervous because he wasn’t ready? Never. Never.”

The way Diaz Sr. sees it, the trek his son has taken to this point is the type that will help him not only become champion, but stay champion.

Russell (28-1, 17 KOs), a fellow southpaw, will be a tough nut to crack. But he is impressed with how badly Diaz wants it.

“I welcome the fact that Diaz wants the fight,” Russell, 29, of Capitol Heights, Md., said. “As a world champion, I wouldn’t want or expect anything less. I want a competitor that’s ready to fight and that’s going to bring their best. I believe that he’s going to be the best that he can possibly be.”

Diaz was stoked to box in the Olympics, but winning a world title as a pro has always been his No. 1 goal. In his mind, his best is going to be better than Russell’s.

“Every single day, I dream about getting my hand raised and defeating Gary Russell,” Diaz said. “And I have no doubt that I’m going to come out victorious come May 19.”